Journal of Entomology and Zoology Studies 2017; 5(3): 91-102 E-ISSN: 2320-7078 P-ISSN: 2349-6800 Life cycle of Papaya mealybug Paracoccus JEZS 2017; 5(3): 91-102 © 2017 JEZS marginatus Williams and Granara de Willink on Received: 15-03-2017 Accepted: 16-04-2017 different host plants vis-à-vis divergent natural R Nisha selection Department of Crop Protection, Imayam Institute of Agriculture and Technology, Thuraiyur, R Nisha and JS Kennedy Trichy JS Kennedy Abstract Department of Agricultural Life cycle of Papaya mealybug PMB Paracoccus marginatus on different host plants was studied using Entomology, Tamil Nadu Age Specific (or Horizontal) and Stage Specific (or Vertical) Life Table. It showed enormous biological Agricultural University, activity of PMB on host plants. The net reproductive rate of papaya mealybug was observed to be higher Coimbatore, India in papaya (559.48 females/female) and least in tapioca (282.53). The capacity for increase (rc) was minimum (0.324) in tapioca and maximum in papaya (0.512). Intrinsic rate of increase (rm) has increased with the increase in the rate of capacity for increase as it was maximum in papaya (0.570 increase per day), minimum in tapioca (0.342/day). The cumulative K value, total generation mortality was observed to be minimum in female than male. It was minimum in papaya 0.0325 for female and 0.0587 for male mealybug, while tapioca recorded highest K value of among the host plants (0.1405 in female and 0.1799 in male). Keywords: Life cycle, life table, survival, mortality, Papaya mealybug, Paracoccus marginatus, natural selection, k value, intrinsic rate, net reproductive rate 1. Introduction A life table is a kind of book-keeping system that ecologists often used to keep track of stage specific mortality in the population they study [13]. A life table describes for successive age intervals, the number of deaths, the survivors, the rate of mortality and the expectation of further life [11]. Life table provides an important tool in understanding the changes in population of insect pests during different developmental stages throughout their life cycle. It is an especially useful approach in entomology, where developmental stages are discrete and [7] mortality rates may vary widely from one life stage to another . It is very useful to analyse the mortality of insect population, to determine key factors responsible for the highest mortality within population. Moreover, various mathematical formulas also indicated for the appropriate evaluation of life fecundity tables, stable age distribution and life expectancy [4]. The construction of several life tables may be possible to prepare a predictive model which can [12] be tested against natural population fluctuations . Life table is an important analytical technique in studying distribution, determination of age and mortality of an organism and individuals can be calculated [11]. On being a polyphagous pest, PMB is feeding on many plants with divergent variation in development and bioecology [14]. Hence, the present research was conducted to study the life cycle of PMB on different host plants and it reported for first time in the current study. 2. Materials and methods The research work was carried out in the Insectary of Department of Crop Protection, Tamil Nadu Agricultural University, Coimbatore and Tamil Nadu, India (Department of Agricultural Entomology and biocontrol laboratory). 2.1. Collection and mass culturing of Paracoccus marginatus Correspondence Potato sprouts was used as an alternate food source for rearing mealybugs. Mass culturing of R Nisha [17] Department of Crop Protection, potato sprouts (Fig. 1) was done in line with the reference of . Papaya mealybugs collected Imayam Institute of Agriculture from different host plants like papaya, tapioca, cotton, mulberry, brinjal and hibiscus were and Technology, Thuraiyur, released on potato sprouts (Fig. 2) using camel hair brush at the rate of 3 to 5 ovisacs per Trichy potato and mealybugs en masse were obtained within 25 to 30 days of release. Mass culturing ~ 91 ~ Journal of Entomology and Zoology Studies Column one of the life table gives the age of life from birth to was also carried out in above said host plants and used for death. The second column shows the survivorship to each age further experiments [2]. The observations needed for the life of life, starting out at birth (age 0), and diminishing from age cycle studies were documented and calculated as below. to age in accordance with the mortality. The figures in this column are generally denoted by the symbol lx. The third column indicates the corresponding survival fraction (Sx) at each interval of life, being simply the fraction between lx of the subsequent stage and lx of the current stage. The fourth column gives the death rate in each day of life or to be more exact, the probability at a given age of dying in an interval, this being denoted by the symbol qx. The figures in the fifth and sixth column are the total number of females produced for total population and number of females produced per female, respectively. The seventh and eighth columns are auxiliary columns employed in computing the ninth column, which gives the expectation of life at each age. The ninth column gives the average number of insects living in each age of life. The figures in this column may also be interpreted as the number of days of life lived within a Fig 1: Mass culturing of papaya mealybug Paracoccus marginatus given age of life. Column eighth is obtained by cumulating on potato sprouts the figures in column seventh beginning at the end. Lastly, column ninth, gives the expectation of life or the average after 2.2. Description of life table statistics lifetime at each age class of life. It is obtained as the quotient Life table describes the mortality and survival patterns of a of the figures in column eighth and the corresponding figures population. On the basis of mortality ratios for each age or in column two, for this gives a total number of age class lived age group, life tables provide information on parameters such by survivors of a cohort after a given age, divided by the as the number of survivors, the number of deaths and the life number of insects entering that age [8]. The 10th and 11th [8] expectancy . columns are auxiliary columns used in the calculation of the th 12 column denoted as intrinsic rate of natural increase (rm). 2.2.1. Construction of age and stage specific life table The life tables for insect species were built by partitioning its life-cycle into distinct development stages (e.g., eggs, larvae, pupae and adults; eggs, nymphs and adults), and by evaluating the development time and survival or mortality for each individual stage. For females, the age-dependent total a) Papaya b) Cotton oviposition (fecundity/reproduction) was also determined. [15] The different life table parameters viz., Survivorship (lx) , Survivorship curves [10], Fixation of survivorship curves [16], Survival fraction (Sx), Apparent mortality, Mortality survivor [18] ratio (MSR), Indispensable mortality (IM), K-values , Net reproductive rate, Intrinsic rate of natural increase, Finite rate of increase (λ), Mean generation time (T), Doubling time of population (t) were calculated as per the earlier experiments [4] [1, 3, 11] c) Tapioca d) Mulberry . 3. Results and Discussion Data on vital schedules such as survival, mortality, and fecundity were collected for papaya mealybug on different host plants. The observations on fecundity and total number of females emerged were recorded from the experiment. By using the above said observations life tables were constructed for mealybugs from different host plants. The stage specific e) Brinjal f) Hibiscus life tables were constructed from the data derived from age specific life tables. 3.1. Age specific life table of Paracoccus marginatus from different host plants The data on the age specific life tables of papaya mealybug from different crops are exhibited in the Tables 1 to 7. The results revealed that the total life span of adult mealybug was g) Potato sprouts minimum and last for 28 days in papaya, while it was Fig 2: Host plants raised in pots for biology and life cycle studies of maximum in tapioca (42 days). In papaya the production of Papaya mealybug Paracoccus marginatus off springs (56 females/female) started from the eighth day th and ceased on 18 day of life span with production of 26 ~ 92 ~ Journal of Entomology and Zoology Studies females per female. The ninth day was the start of First instar (Crawler) 5 days reproduction period in cotton (65 females) and ended with 21 Egg - 8 days females on 19th day with 30 days of adult longevity. In potato sprouts, mealybug started reproduction (56 females) from 9th day and ended up with 22 females on 19th day and the total life span was lasted for 31 days. In mulberry PMB recorded 49 days of females on 10th day st and 10 females on 21 day. The adult longevity was 32 days. Second instar The 10th day was the start of reproduction period in brinjal Total - 3.2 days with production of 44 females per female and ended with 11 Total females on 22nd day and had the life span of 35 days. In Life Cycle hibiscus and tapioca, the reproduction of offsprings (31 and 50 Days 21 females/female) started from the 11th and 13th day and ceased on 23rd and 26th day of their life span (36 days and 42 days respectively) with reproduction of 5 and 2 females per female respectively. Papaya, cotton and potato sprouts recorded higher reproduction of offsprings with lesser Adult Female lifespan and production days. Mulberry was marginally same 16.2 days as that of those crops.